Representation of the effects (sorted by order of importance) of the 4 studied factors (flow rate, temperature, pH, and gradient slope) and p-values (Pr(>t)) of their significance tests for (A) tR(DXM), (B) tR(Imp.A), (C) tR(Imp.C), (D) Imp.A efficiency, (E) Imp.C efficiency, and (F) solvent consumption.